# Backstage: Improper URL validation in catalog entity placeholder resolution

Advisory record · `GHSA-qgvj-qcf8-xq73`

- **Identifiers:** `GHSA-qgvj-qcf8-xq73` · `CVE-2026-106498`
- **State:** Confirmed
- **Severity:** CVSS 7.7 High
- **Critical:** No
- **Weakness (CWE):** [CWE-863](https://cwe.mitre.org/data/definitions/863.html) · [CWE-918](https://cwe.mitre.org/data/definitions/918.html)
- **Tags:** [Broken access control](https://agentprime.io/advisories/tag/access-control.md) · [Server-side request forgery (SSRF)](https://agentprime.io/advisories/tag/ssrf.md)
- **Published:** 7 Oct 2026
- **Updated:** 7 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 7 Oct 2026, 17:59 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `@backstage/plugin-catalog-backend` (npm): affected `<3.9.1`; fixed in `3.9.1`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.7 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0031, the 23rd percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 13:33 UTC: First seen by agentprime
- 31 Oct 2026, 13:33 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-qgvj-qcf8-xq73)

## Sources

- [GitHub Advisory Database: GHSA-qgvj-qcf8-xq73](https://github.com/advisories/GHSA-qgvj-qcf8-xq73)
- [OSV: GHSA-qgvj-qcf8-xq73](https://osv.dev/vulnerability/GHSA-qgvj-qcf8-xq73)
- <https://github.com/backstage/backstage/security/advisories/GHSA-qgvj-qcf8-xq73>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-106498>
- <https://github.com/backstage/backstage/commit/0b0f6fc89b4eb4872c76a498abbe1dc65998bb6e>
- <https://github.com/backstage/backstage/commit/286bfc1f9cc3608a073b41016be302785be385d1>
- <https://github.com/backstage/backstage/commit/61a10f19926aeda7f4a32de48d733e6710584634>
- <https://github.com/backstage/backstage/commit/99729e925fd2bd40ba210022351a0ee6318e6197>
- <https://github.com/backstage/backstage/commit/e786ac309ed2d775daf2309393c015c43902d6f6>
- <https://github.com/backstage/backstage>
- <https://github.com/backstage/backstage/releases/tag/v1.49.6>
- <https://github.com/backstage/backstage/releases/tag/v1.50.5>
- <https://github.com/backstage/backstage/releases/tag/v1.51.3>
- <https://github.com/backstage/backstage/releases/tag/v1.53.2>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-qgvj-qcf8-xq73>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-qgvj-qcf8-xq73/>. Everything for agents: <https://agentprime.io/llms.txt>.